Electric furnace



E. F COLLINS.

ELECTRIC FURNACE.

APPLICATION FILED MAR. I. 1921.

1,432,442. Patented 04 111922;

In ventm FT Ems Patented Oct. 17, 1922.

UNITED STATES PATENT OFFICE.

EDG AR F. COLLINS, OF SCHENECTADY, YORK, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATION OFNEW YORK.

ELECTRIC FURNACE.

Application filed Hara- 1, 1921. Serial No. 448,798.

To all whom it may concern:

Be it known that I, EDGAR F. COLLINS, a citizen of the United States, residin at Schenectady, county of Schenectady, tate of New York, have invented certain new and useful Improvements in Electric Furnaces, of which the following is a specification.

The present invention relates to electric resistance furnaces or ovens. One of the objects of my invention is to provide a more rugged and more efficient form of furnace than has heretofore been produced. Furnaces embodying my invention are adapted for a wide range of industrial operations, particularly for various heat treatments of metals.

One class of furnaces of the resistance type heretofore in use were constructed by winding a refractory wire upon the outside of a tube or muffle. The work to be heated within the mufile was separated from the source of heat by the muflle wall requiring the resistor to be heated to a very much higher temperature than the work. Another class of muflie furnace has been constructed by placing the resistors in grooves or slots in the inner surface of the muflie. Although this method of support gives better thermal efiiciency certain disadvantages are present, particularly local overheating of the resistor and the greater difficulty of manufacture and repair of the furnaces. In both of these prior forms great care was required not to heat up the furnace too rapidly from cold, and to prevent damage to the resistors when the furnace had come up to the operating temperature.

By my present invention I have provided a type of furnace in which the heater is selfsupporting and is placed within direct radiating relation to the charge out of im-,

mediate contact with the furnace wall. Moreover, the heater is a self contained and easily removable from the furnace as a separate unit. The furnace hence can be easily manufactured and reparied. The novel features and advantages of my invention will be pointed out with greater particularity in the appended claims. For a complete description of my invention reference may be had to the accompan ing drawing in which Fig. 1 is a longitu inalsection of a furnace embodying my invention; Fig. 2 is a perspective view of a preferred form of resistor; Fig. 3 is a perspective of the mounting of the heater in the furnace; and Fig. 4 is a detail view of an arched member shown removed from the furnace in Fig. 3.

The furnace shown in Fig. 1 comprises a metal frame 5 consisting conveniently of angle iron suitably bolted and supporting a body of refractory bricks 6. The heating space Within the furnace may be lined in any suitable manner. Preferably, I provide a refractory container 7 having a semicylindrical shape, that is, having a floor and an arch above the floor as this shape gives a high thermal efficiency, the heat being concentrated b reflection and radiation upon the work. ounted within the container is a self-supporting resistance heater consisting of suitable refractory material, for example nichrome, or other high resistance alloy. This resistor preferably is ribbonshaped, and constructed to conform to the general contour of the inner wall of the container, but located out of direct contact with the furnace wall. Although contact at a few points would do no particular harm, I prefer to extend the flat portion of the ribbon away from the furnace wall, that is, to construct the heater of a ribbon bent back and forth upon itself in the shape of a plurality of substantially parallel arches each having substantially the same center of curvature as the arch of the container 7. In the construction illustrated, planes passing through the respective arches are substantially parallel and extend at right angles to the horizontal axis of the container but my invention is not limited to this particular construction.

The arched sections are bound together and spaced apart from one another by 1nsulators 9 which as shown may consist of a number of sections. These insulators have a plurality of outwardly projecting teeth 10 extending between the adjacent resistor arches. A rod consisting of nichrome or other suitable material, the head ll only of which has been shown, may pass through each of the insulators 9 to increase their strength. The base portlons of the insulators 9 slide in slots formed in the wall of the container, as indicated at 12, Fig. 3. The described structure is rugged and thermally eflicient. Heat may be freely radiated from the exposed heater ribbon directly to the work and to the container wall from whence it is reflected back to the work.

lutions and supporting means for said heater adapted to permit slidable disengagement of the heater from the furnace While leaving said furnace structure substantially undisturbed.

13. An electric resistance furnace comprising a refractory container, at self-supporting arched heater comprising a plurality of convolutions, refractory slotted supports 10 in the floor of said furnace extending parallel to each other, and arranged to permit the slidable insertion and withdrawal of the heater with the opposite edges of the heater resting in the slots of said supports and a refractory member locking said heater in position while permitting access to the furnace interior.

In witness whereof, I have hereunto set my hand this 28th day of February, 1921.

EDGAR F. COLLINS. 

